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What is Anaplasmosis? Print E-mail
Written by Dra. Deanne Sharer, Veterinarian   
There is yet another “tick disease” on the scene that I thought might warrant clarifying. As most dog owners in the area have either heard about or dealt with canine ehrlichiosis, there is another strain of the same type of parasite that is now becoming more and more common here in tropical paradise.


As reviewed in a previous article in Zoom, the disease caused by Ehrlichia canis is a very common if not endemic tick borne disease in Costa Rica. Now there is another similar culprit that is every day more prevalent in our area called Anaplasma phagocytophilium. It was previously called Ehrlichia equi, but in the past few years has changed names. Both are intracellular blood parasites transmitted by ticks, the main difference being that Ehrlichia canis infects monocytes and Anaplasma phagocytophylium infects neutrophils (two different types of white blood cells). Although both are treatable with the same protocol, the two don’t always cause the same symptoms, hence the intent of this article is to make dog owners aware of and therefore on the lookout for this “other” tick borne pathogen.


As a general review, the Ehrlichia species are a group of tick-transmitted, intracellular, gram-negative bacteria in the family Rickettsiaceae. The organisms that cause the diseases currently known as canine ehrlichioses are in three genera, Ehrlichia, Anaplasma, and Neorickettsia. These organisms may reside in one or more host blood cell types including granulocytes, monocytes, and platelets. However, eachspecies h as a fairly strong predilection for a specific cell type, thus categorizing most infections as either granulocytic or monocytic ehrlichioses. In addition, one known species infects platelets (Anaplasma platys).


There are several different Ehrlichia species known to infect dogs {E. canis, E. ewingii, Anaplasma platys (formerly E. platys), Neorickettsia risticii (formerly E. risticii), E. chaffeensis, and Anaplasma phagocytophilum (formerly E. equi and the human granulocytic ehrlichia, HGE)}, and the clinical presentations may differ, depending on the organism involved. In our area, however, E. canis and
A. phagocyophilum are the most commonly occurring at this time.

The monocytic form of canine ehrlichiosis is arguably the most common form, caused by E. canis or E. chaffeensis, (the causative agent of Human Monocytic Ehrlichiosis). These intracellular rickettsial agents reside in the mono-cytes of the infected host. The granulocytic Ehrlichioses are caused by organisms thathave a tropism for neutrophils. There are two main organisms that are known to infect dogs, Ehrlichia ewingii, and Anaplasma phagocytophilum. Infection with A. phagocytophilium has been recognized

in a wide variety of hosts including humans, horses, dogs, cats, ruminants and many wild-life species.


Clinical signs can be similar to those seen with E. canis; for example during acute infection animals often have signs of illness including fever, lethargy, malaise and anorexia. However, the most frequently observed clinical findings in dogs that would alert you to A. phagocytophilum infection are joint pain and lameness (resulting from polyarthritis) and general muscle pain resulting in reluctance to move.

It may seem like the dog is paralyzed, especially in the hind quarters. Other less commonly observed clinical signs may include gastrointestinal problems such as vomiting, diar-rhea, or both, or respiratory signs suchas coughing and labored breathing. Central nervous system disease (meningitis) can also occur, resulting in seizure activity, ataxia, or neurologic manifestations such as dullness or stupor, but these findings are infrequently observed.


So if your dog wakes up one day and he can’t walk, be aware that this may be a sign of canine granulocytic ehrlichia (A. phagocytophilium), and it warrants ruling out of the differential diagnosis. It is best treated early as in monocytic ehrlichiosis. If you’re having any questions or this is happening to your dog, please call.


Dra. Deanne Sharer, Medica Veterinaria 8837-8244

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